This invention relates to a rotary positionable installation mounted on the top of a tower and including a housing or apparatus carrier rotatable about the vertical axis of the tower by an azimuth drive unit.
Wind energy or power installations, originally windmills, for the generation of electric power are designed at the present time with substantial dimensions, for example, a reinforced concrete tower of about 120 m height and 3.5 m diameter and a rotor or propeller of 145 m diameter for a rated electrical power of 5 MW, and for a significant service life of more than 20 years, note the company document MBB-Wind Energy Installation WEA 5000 (GROWIAN II), 1979.
In this installation, the tower carries, over a fully rotatable rotary connection, a nacelle or housing as the apparatus carrier with a supporting structure, components, such as an electric generator, and the housing, in turn, supports a rotor or propeller for the conversion of wind power into electrical power. This rotary connection which includes an azimuth drive unit, has an outer ring fixed to the tower with a toothed rim engaged over two pinions by the azimuth drive unit fixed to the housing, for rotating the supporting structure and housing during operation relative to the tower, so that the propeller can follow or track the changing wind directions for obtaining the maximum electrical power from the wind power.
To avoid a slack, that is, a reverse play, as known by the inventor, the azimuth drive unit has two drives arranged in the housing which are braced relative to one another in a known manner, by a braced drive, with the two drives having two identical, multi-step planetary gear units or "cyclo" gear units in a trundle arrangement.
This wind power installation forms in various respects a swinging system which is excited periodically, particularly by the propeller. To prevent destruction or damage to the wind installation, the natural frequencies of the wind power installation must be sufficiently spaced from the exciting frequencies. These natural frequencies cannot be determined exactly when the wind power installation is designed and constructed, that is, the yawing frequencies measured in a known manner after the installation has been constructed differ from the theoretically determined values and, therefore, the wind power installation must be adjusted subsequently during actual operation.
This pertains particularly to the natural yawing frequency, the torsion frequency of the tower. In the past, the adjustment of such natural yawing frequencies had been effected by providing additional weights in the housing spaced as far as possible from the bearing of the rotary connection. These additional weights, however, result in an undesirable increase in the weight supported by the tower and, thus in a reduction of the natural bending frequency of the tower which, in turn, must be corrected as much as possible.
Difficulties similar to those occurring in wind power installations occur generally in all large installations in which rotary positioning is effected on an elevated structure, for example, in a tower mounted crane or a reflector antenna installation, that is, a radio telescope, particularly if a braced gear unit or a trundle is used for this purpose.